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Full vulnerability report · 2021
CVE-2021-42374High confidence

An out-of-bounds heap read in Busybox's unlzma applet leads to information leak and denial of service when crafted LZMA-compressed input is decompressed

busybox · busybox

Official source article: Siemens SSA-831302 ↗. Check the applicable product and release in the original source.

5.3MediumCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 31 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityMediumOperational priority:Medium, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • A structured source references public exploit or proof-of-concept material.
  • Exploitation requires an existing local or physical foothold with privileges.
  • EPSS is 0.62% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict local access and enforce least privilege on affected hosts.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs busybox busybox and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: As exposure requiresRemediation target: Within 365 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 31 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Distribution package intelligence

Release-specific package status

Alpine, Debian findings are scoped to the named distribution, release and source package. An absent finding does not mean a package is unaffected.

7 package states
Repository candidate not checked

A published vendor fix does not prove that a matching update is enabled and installable on a particular asset. Confirm the local package candidate before scheduling remediation.

Distribution releaseSource packageVendor stateFixed versionEvidence
Alpine v3.23v3.23 · mainbusyboxVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.1.34.0-r0Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.22v3.22 · mainbusyboxVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.1.34.0-r0Alpine Security Database ↗Source updated 3 Oct 2026
Alpine v3.21v3.21 · mainbusyboxVendor fix publishedAlpine records a security fix at this version. An absent entry does not mean the package is unaffected.1.34.0-r0Alpine Security Database ↗Source updated 3 Oct 2026
Debian trixietrixie · sourcebusyboxVendor fix publishedDebian records a fixed source-package version for this release.1:1.35.0-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian bookwormbookworm · sourcebusyboxVendor fix publishedDebian records a fixed source-package version for this release.1:1.35.0-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian forkyforky · sourcebusyboxVendor fix publishedDebian records a fixed source-package version for this release.1:1.35.0-1Debian Security Tracker ↗Source updated 5 Oct 2026
Debian sidsid · sourcebusyboxVendor fix publishedDebian records a fixed source-package version for this release.1:1.35.0-1Debian Security Tracker ↗Source updated 5 Oct 2026
Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

4 current
SSA-831302 · CSAF 2.0 · revision 5 · interimSiemens ProductCERTSSA-831302: Vulnerabilities in the BIOS of the SIMATIC S7-1500 TM MFP before V1.3.0
1 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • SIMATIC S7-1500 TM MFP - BIOS
Summary
An out-of-bounds heap read in Busybox's unlzma applet leads to information leak and denial of service when crafted LZMA-compressed input is decompressed. This can be triggered by any applet/format that internally supports LZMA compression.
Remediation
Update to V1.3.0 or later version
SSA-942865 · CSAF 2.0 · revision 2 · finalSiemens ProductCERTSSA-942865: Multiple Vulnerabilities in the Integrated SCALANCE S615 of SINAMICS Medium Voltage Products
1 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • SINAMICS PERFECT HARMONY GH180 6SR5
Summary
An out-of-bounds heap read in Busybox's unlzma applet leads to information leak and denial of service when crafted LZMA-compressed input is decompressed. This can be triggered by any applet/format that internally supports LZMA compression.
Remediation
Update the firmware of the integrated SCALANCE S615 device to V7.2 or later version
SSA-419740 · CSAF 2.0 · revision 1 · finalSiemens ProductCERTSSA-419740: Multiple Third-Party Component Vulnerabilities in RUGGEDCOM and SCALANCE Products before V7.2
20 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • RUGGEDCOM RM1224 LTE(4G) EU (6GK6108-4AM00-2BA2)
  • RUGGEDCOM RM1224 LTE(4G) NAM (6GK6108-4AM00-2DA2)
  • SCALANCE M804PB (6GK5804-0AP00-2AA2)
  • SCALANCE M812-1 ADSL-Router (Annex A) (6GK5812-1AA00-2AA2)
  • SCALANCE M812-1 ADSL-Router (Annex B) (6GK5812-1BA00-2AA2)
  • SCALANCE M816-1 ADSL-Router (Annex A) (6GK5816-1AA00-2AA2)
  • SCALANCE M816-1 ADSL-Router (Annex B) (6GK5816-1BA00-2AA2)
  • SCALANCE M826-2 SHDSL-Router (6GK5826-2AB00-2AB2)
  • SCALANCE M874-2 (6GK5874-2AA00-2AA2)
  • SCALANCE M874-3 (6GK5874-3AA00-2AA2)
  • SCALANCE M876-3 (EVDO) (6GK5876-3AA02-2BA2)
  • SCALANCE M876-3 (ROK) (6GK5876-3AA02-2EA2)
Summary
An out-of-bounds heap read in Busybox's unlzma applet leads to information leak and denial of service when crafted LZMA-compressed input is decompressed. This can be triggered by any applet/format that internally supports LZMA compression.
Remediation
Update to V7.2 or later version
SSA-565386 · CSAF 2.0 · revision 1 · interimSiemens ProductCERTSSA-565386: Third-Party Component Vulnerabilities in SCALANCE W-700 IEEE 802.11ax devices before V2.0
9 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • SCALANCE WAM763-1 (6GK5763-1AL00-7DA0)
  • SCALANCE WAM766-1 (EU) (6GK5766-1GE00-7DA0)
  • SCALANCE WAM766-1 (US) (6GK5766-1GE00-7DB0)
  • SCALANCE WAM766-1 EEC (EU) (6GK5766-1GE00-7TA0)
  • SCALANCE WAM766-1 EEC (US) (6GK5766-1GE00-7TB0)
  • SCALANCE WUM763-1 (6GK5763-1AL00-3AA0)
  • SCALANCE WUM763-1 (6GK5763-1AL00-3DA0)
  • SCALANCE WUM766-1 (EU) (6GK5766-1GE00-3DA0)
  • SCALANCE WUM766-1 (US) (6GK5766-1GE00-3DB0)
Summary
An out-of-bounds heap read in Busybox's unlzma applet leads to information leak and denial of service when crafted LZMA-compressed input is decompressed. This can be triggered by any applet/format that internally supports LZMA compression.
Remediation
Update to V2.0 or later version
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2021-29345

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

Medium technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 31 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

An out-of-bounds heap read in Busybox's unlzma applet leads to information leak and denial of service when crafted LZMA-compressed input is decompressed. This can be triggered by any applet/format that

What

An out-of-bounds heap read in Busybox's unlzma applet leads to information leak and denial of service when crafted LZMA-compressed input is decompressed. This can be triggered by any applet/format that

Why

The product reads data past the end, or before the beginning, of the intended buffer.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.

What

An out-of-bounds heap read in Busybox's unlzma applet leads to information leak and denial of service when crafted LZMA-compressed input is decompressed. This can be triggered by any applet/format that

Why

The product reads data past the end, or before the beginning, of the intended buffer.

How

An attacker operating through local access may attempt exploitation with low privileges. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
local access → Out-of-bounds Read → disrupt the affected service
Attack surface
Local
Privileges required
Low: a basic authenticated account is required
User interaction
None
Attack complexity
High: exploitation depends on specific conditions
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-125 ↗

CWE-125: Out-of-bounds Read. The product reads data past the end, or before the beginning, of the intended buffer.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVLocalAttack vector: The attacker needs local access to the vulnerable system.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CLowConfidentiality impact: A successful attack can cause a limited loss.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
The issue can support a local privilege or sandbox boundary transition; normal system utilities may then be available in the gained context.
Denial of serviceCWE-125Public exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

BSI · German · WID-SEC-2023-1432Siemens SIMATIC S7: Mehrere Schwachstellen

Ein Angreifer aus dem angrenzenden Netzwerk oder ein entfernter, anonymer, authentisierter, physischer oder lokaler Angreifer kann mehrere Schwachstellen in Siemens SIMATIC S7 ausnutzen, um beliebigen Code auszuführen, Sicherheitsmaßnahmen zu umgehen, vertrauliche Informationen offenzulegen, einen Denial-of-Service-Zustand herbeizuführen, seine Privilegien zu erweitern und Daten zu manipulieren.

Official advisory ↗
BSI · German · WID-SEC-2022-2028BusyBox: Mehrere Schwachstellen

Ein entfernter, anonymer oder authentisierter Angreifer kann mehrere Schwachstellen in BusyBox ausnutzen, um einen Denial of Service Angriff durchzuführen, Informationen offenzulegen oder beliebigen Code auszuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20211117Security Bulletin 17 Nov 2021

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 17 Nov 2021, published on 17 November 2021. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0199Multiples vulnérabilités dans les produits VMware

ERecord?id=CVE-2021-38561 Référence CVE CVE-2021-39293 https://www.cve.org/CVERecord?id=CVE-2021-39293 Référence CVE CVE-2021-3995 https://www.cve.org/CVERecord?id=CVE-2021-3995 Référence CVE CVE-2021-3996 https://www.cve.org/CVERecord?id=CVE-2021-3996 Référence CVE CVE-2021-41089 https://www.cve.org/CVERecord?id=CVE-2021-41089 Référence CVE CVE-2021-41091 https://www.cve.org/CVERecord?id=CVE-2021-41091 Référence CVE CVE-2021-4160 https://www.cve.org/CVERecord?id=CVE-2021-4160 Référence CVE CVE-2021-41771 https://www.cve.org/CVERecord?id=CVE-2021-41771 Référence CVE CVE-2021-41772 https://www.cve.org/CVERecord?id=CVE-2021-41772 Référence CVE CVE-2021-42374 https://www.cve.org/CVERecord?id=CVE-2021-42374 Référence CVE CVE-2021-42376 https://www.cve.org/CVERecord?id=CVE-2021-42376 Référence CVE CVE-2021-42378 https://www.cve.org/CVERecord?id=CVE-2021-42378 Référence CVE CVE-2021-42379 https://www.cve.org/CVERecord?id=CVE-2021-42379 Référence CVE CVE-2021-42381 https://www.cve.org/CVERecord?id=CVE-2021-42381 Référence CVE CVE-2021-42382 https://www.cve.org/CVERecord?id=CVE-2021-42382 Référence CVE CVE-2021-42384 https://www.cve.org/CVERecord?id=CVE-2021-42384 Référence CVE CVE-2021-42385 https://www.cve.org/CVERecord?id=CVE-2021-42385 Référence CVE CVE-2021-42386 https://www.cve.org/CVERecord?id=

Official advisory ↗
CERT-FR · French · CERTFR-2025-AVI-0158Multiples vulnérabilités dans les produits NetApp

.netapp.com/advisory/ntap-20211223-0002/ Bulletin de sécurité NetApp NTAP-20230316-0011 du 16 mars 2023 https://security.netapp.com/advisory/ntap-20230316-0011/ Bulletin de sécurité NetApp NTAP-20230706-0008 du 06 juillet 2023 https://security.netapp.com/advisory/ntap-20230706-0008/ Bulletin de sécurité NetApp NTAP-20240415-0013 du 15 avril 2024 https://security.netapp.com/advisory/ntap-20240415-0013/ Référence CVE CVE-2020-16593 https://www.cve.org/CVERecord?id=CVE-2020-16593 Référence CVE CVE-2020-16599 https://www.cve.org/CVERecord?id=CVE-2020-16599 Référence CVE CVE-2021-42373 https://www.cve.org/CVERecord?id=CVE-2021-42373 Référence CVE CVE-2021-42374 https://www.cve.org/CVERecord?id=CVE-2021-42374 Référence CVE CVE-2021-42375 https://www.cve.org/CVERecord?id=CVE-2021-42375 Référence CVE CVE-2021-42376 https://www.cve.org/CVERecord?id=CVE-2021-42376 Référence CVE CVE-2021-42377 https://www.cve.org/CVERecord?id=CVE-2021-42377 Référence CVE CVE-2021-42378 https://www.cve.org/CVERecord?id=CVE-2021-42378 Référence CVE CVE-2021-42379 https://www.cve.org/CVERecord?id=CVE-2021-42379 Référence CVE CVE-2021-42380 https://www.cve.org/CVERecord?id=CVE-2021-42380 Référence CVE CVE-2021-42381 https://www.cve.org/CVERecord?id=CVE-2021-42381 Référence CVE CVE-2021-42382 https://www.cve.org/CVERecord?id=

Official advisory ↗
CERT-FR · French · CERTFR-2023-AVI-0453Multiples vulnérabilités dans les produits Siemens

CVERecord?id=CVE-2021-33574 Référence CVE CVE-2021-33655 https://www.cve.org/CVERecord?id=CVE-2021-33655 Référence CVE CVE-2021-35942 https://www.cve.org/CVERecord?id=CVE-2021-35942 Référence CVE CVE-2021-3759 https://www.cve.org/CVERecord?id=CVE-2021-3759 Référence CVE CVE-2021-38604 https://www.cve.org/CVERecord?id=CVE-2021-38604 Référence CVE CVE-2021-3998 https://www.cve.org/CVERecord?id=CVE-2021-3998 Référence CVE CVE-2021-3999 https://www.cve.org/CVERecord?id=CVE-2021-3999 Référence CVE CVE-2021-4037 https://www.cve.org/CVERecord?id=CVE-2021-4037 Référence CVE CVE-2021-42373 https://www.cve.org/CVERecord?id=CVE-2021-42373 Référence CVE CVE-2021-42374 https://www.cve.org/CVERecord?id=CVE-2021-42374 Référence CVE CVE-2021-42375 https://www.cve.org/CVERecord?id=CVE-2021-42375 Référence CVE CVE-2021-42376 https://www.cve.org/CVERecord?id=CVE-2021-42376 Référence CVE CVE-2021-42377 https://www.cve.org/CVERecord?id=CVE-2021-42377 Référence CVE CVE-2021-42378 https://www.cve.org/CVERecord?id=CVE-2021-42378 Référence CVE CVE-2021-42379 https://www.cve.org/CVERecord?id=CVE-2021-42379 Référence CVE CVE-2021-42380 https://www.cve.org/CVERecord?id=CVE-2021-42380 Référence CVE CVE-2021-42381 https://www.cve.org/CVERecord?id=CVE-2021-42381 Référence CVE CVE-2021-42382 https://www.cve.org/CVERecord?id=

Official advisory ↗
CERT-FR · French · CERTFR-2023-AVI-0220Multiples vulnérabilités dans les produits Siemens

g/CVERecord?id=CVE-2018-12886 Référence CVE CVE-2018-25032 https://www.cve.org/CVERecord?id=CVE-2018-25032 Référence CVE CVE-2019-1071 https://www.cve.org/CVERecord?id=CVE-2019-1071 Référence CVE CVE-2019-1073 https://www.cve.org/CVERecord?id=CVE-2019-1073 Référence CVE CVE-2019-1125 https://www.cve.org/CVERecord?id=CVE-2019-1125 Référence CVE CVE-2021-26401 https://www.cve.org/CVERecord?id=CVE-2021-26401 Référence CVE CVE-2021-4034 https://www.cve.org/CVERecord?id=CVE-2021-4034 Référence CVE CVE-2021-4149 https://www.cve.org/CVERecord?id=CVE-2021-4149 Référence CVE CVE-2021-42373 https://www.cve.org/CVERecord?id=CVE-2021-42373 Référence CVE CVE-2021-42374 https://www.cve.org/CVERecord?id=CVE-2021-42374 Référence CVE CVE-2021-42375 https://www.cve.org/CVERecord?id=CVE-2021-42375 Référence CVE CVE-2021-42376 https://www.cve.org/CVERecord?id=CVE-2021-42376 Référence CVE CVE-2021-42377 https://www.cve.org/CVERecord?id=CVE-2021-42377 Référence CVE CVE-2021-42378 https://www.cve.org/CVERecord?id=CVE-2021-42378 Référence CVE CVE-2021-42379 https://www.cve.org/CVERecord?id=CVE-2021-42379 Référence CVE CVE-2021-42380 https://www.cve.org/CVERecord?id=CVE-2021-42380 Référence CVE CVE-2021-42381 https://www.cve.org/CVERecord?id=CVE-2021-42381 Référence CVE CVE-2021-42382 https://www.cve.org/CVERecord?id=

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2021-015220Busybox における境界外読み取りに関する脆弱性

Busybox には、境界外読み取りに関する脆弱性が存在します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix availability varies by product
Affected
SIMATIC S7-1500 TM MFP - BIOS
Fixed
Update to V1.3.0 or later version
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 15 Nov 2021 · Last source change 3 Nov 2025, 20:34 UTC · CWE-125 · Out-of-bounds Read

CVE recordCVE.org · 5.2
CVSS sourceNIST NVD
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2021-29345
Product sourceVendor CSAF · Siemens ProductCERT
Remediation sourceVendor CSAF · Siemens ProductCERT
CWE sourceCNA
NVD statusNVD modified after enrichment

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    unspecified < 1.34.0 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    unspecified < 1.34.0 · Fixed: Update to V1.3.0 or later version
    Siemens ProductCERT ↗
  2. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    Siemens ProductCERT ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2021-29345↗Siemens ProductCERT security advisory · Siemens SSA-831302↗CISA Vulnrichment SSVC evidence↗Public exploit reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2021-42374 · cve.blacktree.nl